The invention relates to machines for making embossed textile materials, and more particularly to improvements in machines wherein the embossing of a carpet or a like accumulation of loose fibrous material (hereinafter called fleece for short) takes place during advancement through the nip of two embossing rolls.
Commonly owned U.S. Pat. No. 4,627,137 discloses an embossing machine wherein a smoothsurfaced embossing roll cooperates with a second roll having a peripheral surface provided with knobs to condense selected portions of a fleece which is caused to advance through the nip of the two rolls. An advantage of such machines is that the roll which has a smooth peripheral surface can be produced, and its peripheral surface finished, at a relatively low cost. However, such machines also exhibit certain drawbacks, especially as concerns the maximum achievable thickness of the embossed textile material and the quality and condition of the less compacted portions which surround the condensed portions of the fleece.
It was further proposed to advance a fleece through the nip of two embossing rolls each of which is provided with peripheral knobs. The knobs of one of the rolls register, at least in part, with the knobs of the other roll during travel through the nip of the two rolls. This enhances the compacting action upon selected portions of the fleece, namely upon those portions which happen to advance between pairs of registering knobs during travel through the nip. Such embossing apparatus are not capable of producing an embossed textile material having a thickness which exceeds the thickness of the fleece, i.e., the thickness of the starting material. Moreover, the quality (especially the thickness) of compacted portions of the fleece is overly dependent upon the accuracy of finish of knobs on the two embossing rolls. Thus, even minor deviations of the dimensions of knobs on at least one of the rolls from optimum dimensions will result in the making of an embossed textile material wherein the thickness of compacted portions can vary within a rather wide range. In addition, the cost of embossing rolls is high. Still further, elastic deformation of rolls during the passage of fleece through the nip of the rolls also affects the quality of the thus obtained embossed textile material. Such elastic deformation can exert a pronounced influence upon the quality of the textile material in the middle of the nip, and the effect of elastic deformation upon the quality of the embossed textile material is compounded by the weight of the rolls as well as by the sizes of the knobs. Textile materials which can be produced in embossing machines of the just outlined character are disclosed in German Auslegeschriften Nos. 25 18 531 and 25 18 532 of Cumbers et al.
European patent application No. 0 007 665 of Aziz discloses a machine for embossing pretreated textile materials. The machine employs a pair of embossing rolls each of which is provided with knobs, and the knobs on one of the rolls are staggered with reference to knobs of the other roll so that the pretreated textile material which passes through the nip of such rolls is provided with two layers of compacted portions and with compacted intermediate portions which connect the compacted portions of one layer with the compacted portions of the other layer. The clearances between the external surfaces of the knobs and the internal surfaces bounding the complementary depressions for the knobs are dimensioned in such a way that the compacting action upon the intermediate portions of the pretreated textile material which is caused to advance through the nip of the rolls is more pronounced than upon the portions which form the two layers. This adversely affects certain desirable characteristics of the twice treated textile material, particularly the absorbency of intermediate portions and the softness and suppleness of the ultimate product. The starting material is a precompressed layer of nonwoven textile material.